According to the article by Julian Bahmani Who Wins In A Fight, MARVEL or DC? Well in my humble opinion, that depends on the matchup and the situation.
Some heroes are reactionary, like Iron Man, Mr Fantastic, Hawkeye, Green Arrow, and Batman – give them enough time and knowledge of their opponent and they could probably figure out how to beat them but if you just drop them in the middle of nowhere with no prior knowledge of their opponent, they would be in trouble.
Also the battlefield is crucial to most heroes. The Flash is fast but pit him against NorthStar and drop them at 40,000 feet – well NorthStar can fly, The Flash can’t. Wolverine would shred Aquaman, except if they were both dropped in the middle of the ocean.
The matchup is also crucial. Both Mr Fantastic and Batman are excellent tacticians, but in a slugfest, Batman would win. Now pit Batman against TaskMaster or Wolverine and he would lose. Wonder Woman would probably beat She Hulk, but would in turn get fried by Storm or psychically knocked out by Jean Grey. Superman could beat Thor but would get killed by Phoenix or Protesus.
It comes down to your knowledge of all the superheroes. No matter which hero you pick, there are superheroes from both Universes that can beat them in the right setting. So instead let’s try teamups? How about a Storm/Wonder Woman combo? Ironman/Superman combo? Moon Knight/Batman combo? Green Lantern/Nova combo? Even a Aquaman/Namor combo? Maybe even a few movies?